1. Field of Invention
The present invention relates to improved bolted-on automotive gasket assemblies for internal combustion engines, and more particularly to improved gaskets applied between the bottom flange portions of such engines and the oil pan structures secured thereto.
2. Description of the Prior Art
Those skilled in the art will appreciate the difficulty of maintaining a good quality oil seal between the bottom flange of an internal combustion engine and the oil pan secured to the flange. Typically, the pan is secured to a flange which has portions in various planes, some of the portions including semi-cylindrical sealing surfaces, such as, for example, the portion situated at a centrally located rear main bearing cap of a typical vehicle. Indeed, most oil pan covers have two generally longitudinally extending flat flange surfaces which mate with engine mounting flanges, and two generally semi-circular concave ends adapted to accommodate correspondingly convex mating surfaces of a bearing cap and a timing chamber cover, respectively. Thus, the overall environment for sealing oil pan structures is generally difficult at best.
Unitary prior art molded rubber gaskets have been employed to seal such described irregular boundary sealing criteria. However, such gaskets have main body portions defining bolt or fastener apertures and include concave ends for sealing the noted semi-circular ends. Such gaskets are also difficult to install to the extent that they are limp; i.e. without stiffness. Moreover, such gaskets are also prone to splitting problems at the fastener holes.
As a result, traditional gaskets employed to seal such areas have been subject to considerable redesign efforts in recent years, particularly for aftermarket replacements. One replacement application is for an original equipment gasket consisting of a cork material. Gasket materials suggested as replacements have included thermoset or thermoplastic elastomers, or possibly even soft plastic resins, such as unfilled nylon. In any event, the seal must be robust enough to avoid premature deterioration, and must be resilient enough to seal areas that may be quite narrow. In addition, some attention is needed to enhance sealing effectiveness in regions between bolt or fastener apertures, a recognized source of potential leakage.
The present invention is an improved boundary gasket for sealing between flanged portions of axially mated rigid surfaces such as an oil pan and associated engine block. The gasket constitutes a unitary, rectilinearly shaped molded elastomeric sealing body that includes at least one unitary sealing bead on one facial side thereof. The bead is integral with, and extends circumferentially about, the entire boundary of the gasket on said one side. The bead is radially spaced from a plurality of spaced apertures adapted for accommodating passage of bolt members about the gasket body for fastening flanged portions of the oil pan and engine block together. In a preferred embodiment, the bead provides the primary sealing function for the engine block side of the gasket. The gasket incorporates a one-piece circumferentially extending metallic carrier at its radially outermost edge adapted for imparting rigidity to the gasket body for facilitating handling and installation. The carrier, which also acts as a bolt crush limiter, is adhesively bonded to the unitary elastomeric sealing body at the radially outermost edge of the body.
On the oil pan side of the gasket, waffle pattern sealing regions between apertures are particularly designed for sealing against oil pan flanges having undulating or non-flat surfaces, i.e., surfaces incorporating both positive and negative embossments. For this purpose, the side of the gasket adapted to mate against the oil pan flange contains only segmented beads, positioned about the radially inward edges of the bolt apertures. In the preferred embodiment the beads are integrally formed in the elastomeric body of the gasket. Each region of the gasket between the apertures on the oil pan side includes a waffle pattern also integrally formed within the elastomeric body of the gasket, and the segmented beads extend up to and are contiguous with the lateral boundaries of each waffle pattern region. In a preferred form, each waffle pattern region extends longitudinally over at least 75% of the spanned distance between any two bolt apertures.
The sum of the thicknesses of the waffle pattern regions and the at least one continuous bead on the engine block side comprises an axial thickness greater than that of the carrier; thus upon the tightening by bolt members, the elastomeric material of the bead will only be crushed or compressed to the limiting axial thickness of the carrier.
Finally, the same preferred embodiment of the gasket has two longitudinally extending, flat, side portions, with arcuate end portions contiguously joining the side portions for accommodating semi-circular members situated immediately adjacent the oil pan.